1. Field of the Invention
The present invention relates to a wireless local area network (LAN) deploying mobile internet protocol (IP), and more particularly, to an apparatus and method for supporting mobility of a mobile terminal.
2. Related Art
As mobile terminals such as mobile phones, notebook PCs, and personal digital assistants (PDAs) become more popular and widely utilized, development has focused on allowing users to use mobile terminals to access the Internet from anywhere and to enable mobile terminals to communication with each other and/or other computers, fixed and mobile. In particular, many researches have been conducted regarding technology capable of providing seamless communication when a mobile terminal travels among a plurality of networks without restarting its applications and without disrupting any ongoing communications. An example of this technology is known as mobile internet protocol (IP) which is an Internet standards-track protocol used to provide node mobility in the Internet and to define how digital information (which can be grouped into bundles called “packets”) is exchanged between two or more mobile terminals in the Internet.
FIG. 1 is a diagram showing the structure of an example wireless local area network (LAN) environment deploying mobile IP.
Referring to FIG. 1, the wireless LAN environment deploying mobile IP includes a mobile node (MN) 11, a home agent (HA) 12, a foreign agent (FA) 13, and a correspondent node (CN) 14 connected, via a distribution system such as the Internet.
The mobile node (MN) 11 is a host traveling among a plurality of networks. A network to which the mobile node (MN) 11 is first connected is referred to as a “home network”, and the IP address of the mobile node (MN) 11 in the home network is referred to as a “home address.” Such a mobile node (MN) 11 can change its point-of-attachment to the Internet from one network to another while maintaining any ongoing communications and using only its IP home address.
The home agent (HA) 12 is a router having information on the mobile node (MN) 11, situated in the home network of the mobile node (MN) 11. In particular, when the mobile node (MN) 11 moves out of the home network and is positioned in a foreign network, the home agent (HA) 12 relays the communication between the mobile node (MN) 11 and the correspondent node (CN) 14 based on this information.
The foreign agent (FA) 13 is a router which is connected to the mobile node (MN) 11 when the mobile node (MN) 11 moves out of the home network, and is positioned in a foreign network. The IP address of the mobile node (MN) 11 in the foreign network is referred to as a “care of address” (COA). The correspondent node (CN) 14 can be a host, or a client station, communicating with the mobile node (MN) 11.
Referring to FIG. 1, the operations of the wireless LAN environment deploying mobile IP will now be described as follows.
In operation 1, the mobile node (MN) 11 moves out of the home network into a foreign network. In operation 2, the foreign agent (FA) 13 broadcasts an agent advertisement including network information.
In operation 3, the mobile node (MN) 11 receives the agent advertisement broadcast by the foreign agent (FA) 13, when moved into the foreign network, and based on the network information included in the agent advertisement, detects that it is located in a foreign network. Also, the mobile node (MN) 11 obtains a COA, binds the home address and the COA of the mobile node (MN) 11, and registers the binding result in the home agent (HA) 12.
In operation 4, the home agent (HA) 12 transmits a response to the registration requested from the mobile node (MN) 11.
In operation 5, the correspondent node (CN) 14 transmits packets with a destination set to the home address of the mobile node (MN) 11.
In operation 6, the home agent (HA) 12 intercepts all packets destined to the home address of the mobile node (MN) 11, and by setting the COA of the mobile node (MN) 11 as the new destination of the packets, performs tunneling of packets to the mobile node (MN) 11 at its current location, i.e., to the COA of the mobile node 11.
As described above, in order to deploy mobile IP, routers such as the home agent (HA) 12 and the foreign agent (FA) 13 must support the mobile IP, and each mobile node (MN) must include a separate mobile IP module. When an office is built for networking, for example, the router is one of a small number of infrastructure facilities, which can be easily installed to support the mobile IP. However, there are many types of user terminals and network products, and users are usually reluctant to install additional functions that may affect the operation of existing functions. As a result, it can be very difficult to install a mobile IP module in every mobile node.
Because of this problem, the mobile IP has not been widely used, and therefore, new network products have been introduced to provide WLAN services to mobile nodes do not have the mobile IP function. An example of these network products is a WLAN switch from Airespace, Inc., as shown in FIG. 2.
FIG. 2 is a diagram showing the structure of a wireless LAN environment in which typical WLAN switches are installed to monitor the movement of a mobile node between different networks.
Referring to FIG. 2, the wireless LAN environment in which the WLAN switch is installed includes a mobile node 21, general hosts 22, 23, 24, and 26, access points (“APs”) 24 and 27, WLAN switches 28 and 29, and data sensor switches 210 and 211 located in different networks, i.e., a first wireless LAN or a second wireless LAN.
The MAC address of the mobile node 21 is registered in advance in the WLAN switches 28 and 29. The WLAN switches 28 and 29 are connected to the first wireless LAN and the second wireless LAN, respectively, to detect the movement of the mobile node 21 by referring to the MAC address and perform tunneling between the WLAN switches 28 and 29.
However, even when the WLAN switches are used, supporting the mobility of the mobile node 1 can only be made possible in an area in which a device such as the WLAN switch is installed, and can not be made possible in other types of WLAN environments, such as, Bluetooth. Moreover, it is very inconvenient to register the MAC address of the mobile node 21 in advance in the WLAN switches 28 and 29.
Accordingly, there is a need to create a wireless LAN environment deploying mobile IP in which a mobile node can travel among a plurality of networks while maintaining any ongoing communications seamlessly, even when a mobile IP module is not installed therein.